Assuming you have configured ADV7610 correctly and video is being received and output correctly, then writing:
* ADV7611 CP map 0x7C = 0xC0
and
* ADV7611 CP map 0x7E = 0x01
should shift START_HS by one pixel.
Please note that you will need to write the most significant bits (0x7C) and then write the least significant bits (0x7E) sequentially in order for the value to be latched correctly.
-Matt